Bi-quadratic magnetoelectric coupling in underdoped La_2CuO_{4+x}

The recent discovery of relaxor ferroelectricity and magnetoelectric effect in lightly doped cuprate material La_2CuO_{4+x} has provided a number of questions concerning its theoretical description. It has been argued using a Ginzburg-Landau free energy approach that the magnetoelectric effect can be explained by the presence of bi-quadratic interaction terms in the free energy. Here, by using the same free energy functional, we study the variety of behavior which can emerge in the electric polarization under an external magnetic field. Subsequently, we discuss the role of Dzyaloshinskii-Moriya interaction in generating this magnetoelectric response. This work is particularly relevant for such relaxor systems where the material-dependent parameters would be affected by changes in e.g. chemical doping or cooling rate.Comment: 8 pages, 2 figures. arXiv admin note: text overlap with arXiv:1112.152

Frustration of the interlayer coupling by mobile holes in La2-xSrxCuO4 (x<0.02)

We have studied the interlayer coupling in the antiferromagnetic (AF) phase of Sr and Zn doped La2CuO4 by analyzing the spin flip transition in the magnetization curves. We find that the interlayer coupling strongly depends on the mobility of the hole charge carriers. Samples with the same hole content as well as the same Neel temperature but a different hole mobility, which we adjusted by Zn co-doping, can have a very different interlayer coupling. Our results suggest that only mobile holes can cause a strong frustration of the interlayer coupling.Comment: 4 pages, 4 figure

Magnetic susceptibility anisotropies in a two-dimensional quantum Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions

The magnetic and thermodynamic properties of the two-dimensional quantum Heisenberg antiferromagnet that incorporates both a Dzyaloshinskii-Moriya and pseudo-dipolar interactions are studied within the framework of a generalized nonlinear sigma model (NLSM). We calculate the static uniform susceptibility and sublattice magnetization as a function of temperature and we show that: i) the magnetic-response is anisotropic and differs qualitatively from the expected behavior of a conventional easy-axis QHAF; ii) the Neel second-order phase transition becomes a crossover, for a magnetic field B perpendicular to the CuO(2) layers. We provide a simple and clear explanation for all the recently reported unusual magnetic anisotropies in the low-field susceptibility of La(2)CuO(4), L. N. Lavrov et al., Phys. Rev. Lett. 87, 017007 (2001), and we demonstrate explicitly why La(2)CuO(4) can not be classified as an ordinary easy-axis antiferromagnet.Comment: 6 pages, 3 figures, Revtex4, accepted for publication in Phys. Rev.

Perilaku Dan Motivasi Komplain Konsumen Terhadap Restoran-restoran Di Surabaya

Penelitian ini ditunjukan untuk menguji perilaku, motivasi komplain, serta korelasi antara perilaku komplain dengan usia, jenis kelamin, dan tingkat pendidikan. Uji mean dilakukan untuk menguji tingginya perilaku komplain konsumen dan motivasi komplain konsumen dalam melakukan komplain dan uji chi square untuk menguji adanya korelasi antara perilaku komplain dengan usia, jenis kelamin, dan tingkat pendidikan. Berdasarkan hasil tes dapat disimpulkan bahwa: (1) Perilaku menceritakan pengalaman dan motivasi mengekspresikan emosi yang mana ditunjukkan dari hasil mean yang paling tinggi. (2) Usia tidak berkorelasi dengan perilaku komplain, sedangkan jenis kelamin dan tingkat pendidikan memiliki korelasi

Influence de la rotation culturale, de la fertilisation et du labour sur les populations de nématodes phytoparasites du sorgho (Sorghum bicolor (L.) Moench)

Influence of crop rotation, fertilization and tillage on populations of plant parasitic nematodes of sorghum (Sorghum bicolor (L.) Moench). The soil nematodes of three long-term trials (1960, 1980 and 1990) representing the production of sorghum (Sorghum bicolor (L.) Moench) under different agricultural practices (rotation, tillage and fertilization) in the Center West of Burkina Faso, have been explored in the wake of the harvest during the agricultural season 2007/2008. The objective was to identify these nematodes and to study the influence of agricultural practices on this nematofauna. Nematodes were extracted by the method of Seinhorst elutriator. Plant-parasitic nematodes identified are Pratylenchus brachyurus, Tylenchorhynchus martini, Helicotylenchus multicinctus, Scutellonema Caveness, Criconemoides curvatum, Telotylenchus indicus and Xiphinema sp. The first three species represent approximately 98% of individuals surveyed. On the first site, the treatments involving mineral fertilizer and recycling of sorghum straw were favorable for the control of nematodes instead of treatments involving manure. As for rotations, monoculture of sorghum was more infested by nematodes than the rotations sorghum – cowpea and sorghum – cotton. On the second site, the nitrogen has increased of infestation by the two major nematodes in comparison to treatments without nitrogen, with the exception of treatment with anaerobic compost incorporation. On the third site, deep plowing has been unfavorable to the main nematode sorghum compared to shallow tillage. The nematofauna in fallow was more diversified than in cultivated sites and P. brachyurus, the main nematode related to sorghum has fallen sharply in fallow

Etude des nématodes phytoparasites du sol et des racines sous quatre niveaux de fertilisation minérale en culture de niébé

Les nématodes du sol et des racines ont été étudiés dans 42 exploitations paysannes utilisant quatre (04) niveaux de fertilisation NPK (14-23-14) en production de niébé (Vigna unguiculata (L.) Walp). Les exploitations paysannes sont situées dans les villages de Saria, Villy et Godin dans le Centre Ouest du Burkina Faso. L’objectif était d’étudier la dynamique des nématodes sous l’influence des pratiques agricoles différentes. Les nématodes du sol et des racines ont été extraits respectivement par les méthodes de l’élutriateur Seinhorst et de l’appareil asperseur de Seinhorst. Dans les différentes exploitations de niébé, 07 espèces de nématodes phytoparasites du sol ont été recensées. Il s’agit des espèces suivantes : Pratylenchus brachyurus, Helicotylenchus multicinctus, Scutellonema cavenessi, Tylenchorhynchus martini, Xiphinema sp., Telotylenchus indicus et Criconemoïdes curvatum. Parmi elles, H. multicinctus et Scutellonema cavenessi représentent la grande majorité des individus. Les nématodes dans les racines du niébé sont représentés principalement par trois espèces : T. multicinctus, S. cavenessi et P. brachyurus avec des taux d’infestation de 0 à 6 N/g de racines. L’utilisation de la fumure minérale n’a pas eu d’influence sur les nématodes dans le sol mais elle a fait baisser la pression des nématodes sur les racines des cultures.Mots clés : Niébé, nématode phytoparasite, racine, fumure minérale

Influence de la rotation culturale avec apport de matières organiques exogènes et d’une fertilisation minérale sur les nématodes phytoparasites en culture du sorgho au Centre Ouest du Burkina Faso

L&#8217;infestation du sol et des racines du sorgho (sorghum bicolor (L.) Moench) par les n&#233;matodes phytoparasites a &#233;t&#233; &#233;tudi&#233;e en 2008 sur un essai agricole &#224; l&#8217;Ouest du Burkina Faso. Cet essai agricole est repr&#233;sentatif de la production du sorgho avec utilisation de diff&#233;rentes pratiques agricoles incluant la rotation culturale, l&#8217;apport de mati&#232;res organiques exog&#232;nes et une fertilisation min&#233;rale. L&#8217;objectif &#233;tait de d&#233;terminer l&#8217;effet de ces pratiques sur les taux d&#8217;infestation du sol et des racines par les n&#233;matodes. Les n&#233;matodes du sol ont &#233;t&#233; extraits selon la m&#233;thode de &#171; l&#8217;&#233;lutriateur &#187; de Seinhorst et ceux des racines selon la m&#233;thode de &#171; l&#8217;asperseur &#187; de Seinhorst. Le sol et les racines du sorgho ont &#233;t&#233; plus infest&#233;s par les n&#233;matodes dans la monoculture de sorgho par rapport aux rotations sorgho &#8211; ni&#233;b&#233; et sorgho &#8211; coton. Les traitements incluant la mati&#232;re organique et la fertilisation min&#233;rale ont &#233;t&#233; moins infest&#233;s par les n&#233;matodes par rapport aux traitements utilisant uniquement une fertilisation min&#233;rale. La n&#233;matofaune de la jach&#232;re a &#233;t&#233; plus diversifi&#233;e que celle du site cultiv&#233; et le principal n&#233;matode li&#233; au sorgho, P. brachyurus, y a fortement r&#233;gress&#233;.Mots cl&#233;s: rotation, fertilisation min&#233;rale, mati&#232;re organique, n&#233;matode

CT dose reduction factors in the thousands using X-ray phase contrast

Phase-contrast X-ray imaging can improve the visibility of weakly absorbing objects (e.g. soft tissues) by an order of magnitude or more compared to conventional radiographs. Previously, it has been shown that combining phase retrieval with computed tomography (CT) can increase the signal-to-noise ratio (SNR) by up to two orders of magnitude over conventional CT at the same radiation dose, without loss of image quality. Our experiments reveal that as radiation dose decreases, the relative improvement in SNR increases. We discovered this enhancement can be traded for a reduction in dose greater than the square of the gain in SNR. Upon reducing the dose 300 fold, the phase-retrieved SNR was still almost 10 times larger than the absorption contrast data. This reveals the potential for dose reduction factors in the tens of thousands without loss in image quality, which would have a profound impact on medical and industrial imaging applications